Since surface plasmon resonance (SPR) spectroscopy is in widespread use for probing interfacial phenomena according to measurement of minute changes in charge density wave of free electrons within a metal film, the experimental configuration for SPR sensing can be applied to a thin noble metal film and the flat surface of a prism in which polarized light of a single wavelength is introduced at an angle, so that internal reflectance is achieved. It plays an important role of probing interaction between molecules and also provides label-free bio-sensing for probing the affinity between biological molecules. However, a standard SPR biosensor is designed according to the measurement and recording of the reflected light, and a shift in the angle of the incident beam corresponding to optimal surface plasmon coupled with the metal film is generated. Consequently, the foregoing optical setup is expensive, inconvenience and difficult to be miniaturized.